Tropical Cyclone Discussion
374 WTPZ42 KNHC 262034 TCDEP2 Tropical Storm Vance Discussion Number 22 NWS National Hurricane Center Miami FL EP222026 200 PM MST Mon Oct 26 2026 The structure of Vance hasn't changed much since the previous advisory. Visible satellite imagery is consistent with recent microwave fixes that the center is near the western edge of the main convective area. The initial intensity will again be held at 55 kt, which is supported by the latest TAFB current intensity estimate and recent DMINT intensity estimates. Vance has been jogging toward the west today, with the current motion estimated at 280/5 kt. A slow west-northwestward track is expected over the next 24 hours or so due to a weak mid-level ridge to the north of the system. By Wednesday, a broad mid-level trough near the Baja California peninsula should induce a turn toward the north. The NHC track forecast has again been shifted slightly to the west of the previous one, and is in between the latest GDMI and HCCA forecasts. It should be noted that there is considerable spread/uncertainty in the timing/forward speed of Vance after it makes the northward turn, with the HAFS and ECMWF faster to the north, while the GFS and GDMI show a slower northward motion. The NHC forecast is a little on the slower side compared to some of the guidance but is faster than the GDMI. Although Vance remains in a favorable thermodynamic environment with warm water and enough atmospheric moisture, the cyclone is experiencing moderate to strong west-southwesterly wind shear. The wind shear is forecast to increase a bit more (to near 25 kt) by hour 12, and this should be enough to cause gradual to steady weakening over the next day or so. On Wednesday, as Vance turns northward and gets closer to the broad trough over Baja California and the subtropical jet, the west-southwesterly vertical wind shear increases to over 35 kt, and is forecast to increase further on Thursday. Surprisingly, most of the models hold onto this system as a tropical storm for a couple more days. The NHC intensity forecast is similar to the previous one, and lies in the middle to lower portion of the guidance envelope. It is likely that Vance's convection will be sheared off by 72 hours, and the NHC forecast shows Vance degenerating to a post-tropical remnant low around that time. All of the models show the low-level circulation of Vance dissipating before day 4, so the timing of dissipation has been moved up to day 4 in the official forecast, which is before the circulation reaches the coast of Mexico. Key Messages: 1. Periods of heavy rainfall associated with Vance will impact portions of western Mexico during much of this week. This rainfall may produce flooding and mudslides across southern Sinaloa, southwest Durango and coastal sections of Nayarit, Jalisco, Colima and Michoacan, especially in areas along steep terrain. 2. Although the wind threat to southwest Mexico is decreasing as the forecast track shifts westward away from the coast, interests there should continue to monitor Vance's progress. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 15.4N 106.1W 55 KT 65 MPH 12H 27/0600Z 15.6N 106.9W 50 KT 60 MPH 24H 27/1800Z 16.7N 107.9W 45 KT 50 MPH 36H 28/0600Z 18.1N 108.4W 40 KT 45 MPH 48H 28/1800Z 19.8N 108.6W 40 KT 45 MPH 60H 29/0600Z 21.3N 108.4W 35 KT 40 MPH 72H 29/1800Z 22.6N 108.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 30/1800Z...DISSIPATED